Using thousands of photographs of the Croatian city of Dubrovnik, a software program has created a beautiful, 3D rendering of the city. It looks like impressionist art, but it represents a major breakthrough in how computers process images.

A group of researchers with University of Washington's graphics and imaging laboratory (GRAIL) wanted to see if they could build a piece of software that would search the web for images of a particular place and recreate that place in 3D in under a day. They succeeded. Rome was their first target, since it is such a well-photographed city. Their software harvested images from photo-sharing site Flickr, and recreated landmarks from around the city by determining the angles at which each photograph had been shot and arranging the images accordingly.

But my favorite subject was the city of Dubrovnik, because they managed to get the entire old city - apparently, it's such a well-photographed region that they were able to get all the buildings and streets, instead of just prominent landmarks.

The researchers write:

At the time of our experiments, there were only 58,000 images of Dubrovnik on Flickr. For this city we were able to experiment with the entire collection. Matching took only 5 hours on 352 compute cores. The largest and most interesting component corresonds to the old city. It is interesting that the reconstruction time for Dubrovnik is so much more than that for Rome. The reason lies in how the data sets are structured. The Rome data set is essentially a collection of landmarks which at large scale have a simple geometry and visibility structure. The largest connected component in Dubrovnik on the other hand captures the entire old city. With its narrow alley ways, complex visibility and widely varying view points, it is a much more complicated reconstruction problem, and this is reflected in the time it took to solve it.

Also worth noting is the fact that the reconstruction is not restricted to the city itself, as can be seen in the video below, it also contains the hills surrounding the city and part of Lokrum island which is south east of the city.

There is something poetic about the results of this research. What we are seeing here, in blurred and softened detail, is a concatenation of what thousands of people saw through their camera lenses in Dubrovnik. It's like the GRAIL researchers have given us a way to rebuild cities out of our own memories - at least, if you consider that tourist photographs are one way we remember where we've been.